نشخوار فکری آینده نگر پیش بینی کننده اختلال عملکرد اجرایی در نوجوانان

Background and objectives The current study tested the resource allocation hypothesis, examining whether baseline rumination or depressive symptom levels prospectively predicted deficits in executive functioning in an adolescent sample. The alternative to this hypothesis was also evaluated by testing whether lower initial levels of executive functioning predicted increases in rumination or depressive symptoms at follow-up. Methods A community sample of 200 adolescents (ages 12–13) completed measures of depressive symptoms, rumination, and executive functioning at baseline and at a follow-up session approximately 15 months later. Results Adolescents with higher levels of baseline rumination displayed decreases in selective attention and attentional switching at follow-up. Rumination did not predict changes in working memory or sustained and divided attention. Depressive symptoms were not found to predict significant changes in executive functioning scores at follow-up. Baseline executive functioning was not associated with change in rumination or depression over time. Conclusions Findings partially support the resource allocation hypothesis that engaging in ruminative thoughts consumes cognitive resources that would otherwise be allocated towards difficult tests of executive functioning. Support was not found for the alternative hypothesis that lower levels of initial executive functioning would predict increased rumination or depressive symptoms at follow-up. Our study is the first to find support for the resource allocation hypothesis using a longitudinal design and an adolescent sample. Findings highlight the potentially detrimental effects of rumination on executive functioning during early adolescence.

Major depressive disorder (MDD) is a common and debilitating mental illness with an estimated lifetime prevalence in the United States of 16.2% (Kessler, Merikangas, & Wang, 2007). It is particularly important to study the onset of depression during adolescence as the majority of adults with MDD experience their first depressive episode during this critical period of development (Kim-Cohen et al., 2003). Although rates of depression may be as low as 1% in children up to age 11, a dramatic spike in onset occurs during adolescence, with lifetime prevalence rising to an estimated 5% by age 15 and 20% by age 18 (Hankin et al., 1998). Individuals with depression often report decreased concentration and memory, and cognitive difficulties are an established symptom of MDD (American Psychiatric Association, 2000 and Gotlib and Joormann, 2010). Indeed, depression has been linked to impaired performance on cognitive tasks involving non-emotionally-valenced stimuli; deficits have been found in samples of depressed adults across all domains of executive functioning (EF) including attentional switching, updating and monitoring working memory, and selective attention (Castaneda et al., 2008, Gotlib and Joormann, 2010, Miyake et al., 2000 and Wagner et al., 2011). Findings in adolescent samples have been mixed. Unipolar depression in adolescence has been linked to poorer performance on neutral tests of sustained attention (Maalouf et al., 2011 and Wilkinson and Goodyer, 2006), selective attention (Wilkinson & Goodyer, 2006), and attentional switching (Gunther et al., 2011 and Wilkinson and Goodyer, 2006), as well as working memory (Klimkeit et al., 2011 and Matthews et al., 2008). However, some studies of EF in depressed adolescents have found no difference between depressed and non-depressed youth (Favre et al., 2009 and Gunther et al., 2004), suggesting that further research is necessary. Cognitive impairments observed in depressed individuals may be related to cognitive vulnerabilities. Rumination, a cognitive vulnerability for depression, is characterized by recurring, perseverative thoughts about the symptoms, causes, and future repercussions of one's depression (Nolen-Hoeksema, 1991, Nolen-Hoeksema et al., 2008 and Smith and Alloy, 2009). Rumination has been found to predict the onset (Just & Alloy, 1997), duration (Roberts, Gilboa, & Gotlib, 1998), and number (Spasojevic & Alloy, 2001) of depressive episodes in adult samples. Rumination was also a significant predictor of depressive symptoms (Abela and Hankin, 2011, Nolen-Hoeksema et al., 2008 and Roelofs et al., 2009) and episodes (Abela & Hankin, 2011) in studies of adolescents and children. Rumination also has been linked to impaired cognitive processing on neutral tasks (Wisco & Nolen-Hoeksema, 2008). Dysphoric adults instructed to ruminate displayed inhibition impairments on the Stroop task (Philippot & Brutoux, 2008), as well as poorer short-term problem-solving abilities and impaired concentration (Lyubomirsky et al., 2003 and Lyubomirsky and Nolen-Hoeksema, 1995); the latter two effects did not emerge in nondysphoric participants, or when dysphoric participants were instructed to engage in distraction techniques. In addition to studies of rumination induction, trait rumination also has been associated with cognitive impairments on neutral tasks. Adults scoring higher in rumination were worse at inhibiting a previous task's instructions when presented with a new task; this result was independent of depression score (Whitmer & Banich, 2007). In addition, rumination has been linked to difficulties in attentional switching and mental flexibility in studies examining depressive symptoms in adults (Altamirano et al., 2010, Davis and Nolen-Hoeksema, 2000 and De Lissnyder et al., 2010). Findings of switching deficits complement the conceptualization of rumination as involving difficulties disengaging from depressive cognitions, resulting in repetitive, maladaptive thought patterns (Davis & Nolen-Hoeksema, 2000). In addition, tasks requiring attentional switching and inhibition may be particularly cognitively demanding, in accord with hypotheses that the detrimental effects of rumination on EF may only emerge when under significant cognitive load (Levens, Muhtadie, & Gotlib, 2009). Rumination also has been associated with working memory deficits (Berman et al., 2011 and Meiran et al., 2011). Only one study has examined the relationship between trait rumination, depression and EF in an adolescent sample; whereas attentional switching impairments were linked to MDD, there was no significant relationship between switching and trait rumination (Wilkinson & Goodyer, 2006). In sum, findings from adult and adolescent studies suggest a link between depression and cognitive impairment, particularly with regards to attentional processes and working memory on neutral tasks. Rumination has been associated with similar EF impairments in adults in domains such as attentional switching, inhibition, and working memory, and may in part be responsible for the deficits observed in relation to depression (Gotlib and Joormann, 2010, Hertel, 1998, Levens et al., 2009 and Watkins and Brown, 2002). However, the nature of the relationship between depression, rumination, and executive functioning is not well understood. Resource allocation theory posits that the negative thoughts of depression and rumination deplete limited cognitive abilities that would otherwise be directed towards task-relevant processes (Gotlib and Joormann, 2010, Levens et al., 2009 and Watkins and Brown, 2002). According to this theory, valuable cognitive resources are allocated towards irrelevant depressive and ruminative thought processes. Indeed, depression and rumination have been associated with increased attention towards, and difficulty disengaging from, negative information, as put forward in the affective interference hypothesis (Gotlib and Joormann, 2010 and Siegle et al., 2002). In line with this hypothesis, EF deficits observed in depressed and ruminative individuals may be more indicative of difficulties in cognitive control and attentional redirection than of global processing deficits (Gotlib and Joormann, 2010 and Siegle et al., 2002). At the same time, although engaging in depressive and ruminative thoughts may deplete cognitive resources that would otherwise be directed towards relevant tasks, it is also possible that underlying cognitive impairments could be the cause of depressive and ruminative styles, or that these negative thought patterns and EF impairments interact (Gotlib and Joormann, 2010, Koster et al., 2011 and Levens et al., 2009). Unfortunately, there is a lack of longitudinal research attempting to better understand the direction of the relationship between rumination, depression, and EF impairment. Zetsche and Joormann (2011) found that impaired inhibition of negatively-valenced stimuli predicted increased rumination and depressive symptoms in adults at six-month follow-up; however, this study did not include non-emotional stimuli. De Lissnyder et al. (2012) utilized both emotional and non-emotional stimuli in a longitudinal study examining the relationship between EF, stress, and rumination in college students. They found that baseline emotional set-switching impairments moderated the effect of a stressful life event on subsequent brooding rumination, with higher levels of initial set-switching impairment resulting in higher rumination levels following the experience of a stressor. Interestingly, only emotional set-switching impairments significantly moderated the effect of stress on rumination; non-emotional switching impairments did not. Although these findings tentatively suggest that impaired processing of emotional information may play a role in the development of rumination, the relationship between rumination and non-emotional cognitive processing remains unclear. Several prospective studies have linked rumination and depression in adolescence to lower levels of effortful control (EC), an aspect of temperament encompassing overall self-regulatory and attentional abilities (Hilt et al., 2012 and Verstraeten et al., 2009). Associations have been found between low EC, rumination, and depressive symptoms both concurrently (Verstraeten et al., 2009) and prospectively (Hilt et al., 2012 and Verstraeten et al., 2009), suggesting that lower levels of EC may predict greater rumination and that higher EC may serve as a protective factor against depressive symptoms, although null results also have been reported (Mezulis, Simonson, McCauley, & Vander Stoep, 2011). Findings from studies of EC suggest that the direction of the relationship between underlying cognitive abilities and rumination may be opposite to that proposed by the resource allocation hypothesis, underlining the need for additional longitudinal research. Additionally, the temperamental construct of effortful control in these studies is often measured by self-report, and does not address specific domains of executive functioning, which may be best examined using behavioural methods. To our knowledge, no prospective studies of rumination, depression, and behavioural indices of executive functioning have been conducted in an adolescent sample. From a developmental perspective, it is particularly important to investigate the relationship between rumination, depression, and EF during adolescence. Adolescence is characterized by dramatic rises in depression (Hankin et al., 1998) and increases in rumination (Jose & Brown, 2008). Cognitive styles such as rumination have been hypothesized to undergo consolidation during this period (Alloy & Abramson, 2007), and the association between rumination and depressive symptoms has been found to increase in stability (Rood, Roelofs, Bögels, Nolen-Hoeksema, & Schouten, 2009). In addition, adolescence is characterized by the ongoing maturation of the prefrontal cortex and executive functioning abilities (Alloy and Abramson, 2007, Cicchetti and Rogosch, 2002, Jacobs et al., 2008 and Steinberg, 2008), which continue to develop into mid-adolescence or beyond (Luna and Sweeney, 2004 and Steinberg, 2008). Importantly, EF domains have been found to follow unique developmental trajectories and develop at different rates, with some coming online by early adolescence and others continuing to develop into adulthood (for reviews see Anderson, 2002, Diamond, 2002, Luna et al., 2004, Spear, 2010 and Steinberg, 2008). Although studies examining developmental changes in performance on tests of EF over short time increments during adolescence are relatively rare, there is evidence that development may occur rapidly in some domains. For example, children age 11–12 have been found to differ from children age 13–15 on tests of working memory (Conklin, Luciana, Hooper, & Yarger, 2007), and 15 year-olds have shown superior performance relative to 11 year-olds on aspects of the Wisconsin Card Sorting Test, a complex test requiring cognitive flexibility (Huizinga & van der Molen, 2007). Performance on a variety of tasks, including those assessing switching abilities, has been found to differ in children between ages 11 and 15 (Huizinga, Dolan, & Van der Molen, 2006). Within this developmental context, a complex interplay between depression, rumination, and executive functioning is likely to occur. Consistent with the resource allocation hypothesis, it is possible that increases in rumination and depression occurring during adolescence may interfere with normative development of executive skills. Thus, adolescents who ruminate may fail to achieve expected gains in executive function over time. These adolescents may exhibit weaker EF relative to their same-aged peers as a result of habitual rumination. An alternative possibility is that relative weaknesses in executive functions may emerge during the transition to adolescence, when some adolescents may experience lags in cognitive development relative to their same-aged peers. Adolescents with relative weaknesses in EF may subsequently experience greater difficulty engaging in self-regulation and the redirection of attentional resources, thus leading to increases in rumination. In the current study, we employed a longitudinal design to test whether higher levels of rumination and depressive symptoms at baseline would prospectively predict impaired executive functioning abilities on neutral tests of attention and memory in adolescents. According to the resource allocation hypothesis, habitually engaging in ruminative or depressive thoughts will deplete cognitive resources that would otherwise be directed towards neutral EF tasks. The current study sought to test this hypothesis against the alternate possibility that lowered executive functioning abilities may predict increases in rumination or depressive symptoms at follow-up. These questions were explored using a range of behavioural measures of EF previously demonstrated to be associated with rumination and/or depressive symptoms, including selective attention, sustained attention, attentional switching, divided attention, and working memory. We chose to examine multiple EF domains, given evidence that rumination and depression may exhibit dissociable patterns of association with EF measures (Altamirano et al., 2010). The current study expands on previous research by: 1) examining both the resource allocation hypothesis and its alternative using a prospective design and 2) utilizing an adolescent sample and behavioural measures of executive functioning. By employing measures of EF that controlled for age, we sought to examine the effects of rumination and depression on cognitive functioning over time while accounting for normative cognitive development occurring during adolescence.